64 H. M. BERNAPtD. 



fibres/' i.e. streams of mntter passinpf through the inner 

 reticular layer, in this eye, is just what we should expect, in 

 view of the fact that for some days prior to excision it had 

 not been exposed to light; but it is surprising that there 

 should be no traces of any permanent rearrangement of the 

 cytoplasmic reticulum so as to form continuous radial lines. 

 It is possible that this only takes place in very old eyes, when 

 both nuclei and cytoplasmic framework, all but its radial 

 strands, seem to be disappearing (cf. the general condition 

 of the inner reticular layer in fig. 32, a, with that in 32, h). 



In the baboon's retinas, through which an enormous 

 quantity of matter can be seen to have been passing, and in 

 which the large inner limbs are filled with the same matter, 

 all of it the same colour as the pigment, the conditions are as 

 follows : — In the youngest retina (three months) thick 

 yellowish-brown streams in immense numbers pass radially 

 through the compact middle nuclear layer, but when they 

 reach the inner reticuhir layer by far the greater number 

 disappear; the few which seem to run straight through 

 that layer, on examination with a high power, are seen to have 

 a very zigzag and interrupted course. On the inner side of 

 this layer dense streams again form and run towards the inner 

 limiting membrane, expanding and losing their intensity 

 before reaching it. 



In this young baboon's eye, then, there are no clear radial 

 arrangements of the fibres of the inner reticular layer which 

 could, even under the most strained interpretation, be re- 

 garded as susteutacular. 



In an adult male baboon the same is true, only the pigment 

 is blackish. We again see what was described above for 

 other retinas, that the reticulum of the inner reticular layer 

 has become much coarser than in the younger eye, and 

 consequently the zigzag of those streams which run con- 

 tinuously through is much more pronounced. 



In an ''old, very large male^' the streams are still fewer 

 in the inner reticular layer, apparently because every strand 

 is clotted with pigmented matter^ as is also every strand and 



